A turbocharger may be coupled to an engine to increase engine performance. A turbine within the turbocharger converts exhaust energy into rotational energy, and the rotational energy is transferred to a compressor which may increase air flow into the engine. At higher engine speeds and loads, the amount of engine exhaust gas energy output may reach a level that provides more air flow from the turbocharger compressor into the engine than is desired. One way to limit air flow (e.g. boost) into the engine is to bypass a portion of exhaust gas around the turbine so that less exhaust energy is available to rotate the turbine and compressor. The amount of exhaust gas passing through the bypass may be controlled via a waste gate. One type of waste gate may be vacuum actuated. However, vacuum actuation may be an issue when the engine's intake manifold is frequently filled with a positive pressure. For example, small displacement engines may operate with positive intake manifold pressures to meet driver demand torque. Since a positive pressure is greater than atmospheric pressure, vacuum is not produced in the engine's intake manifold and sufficient vacuum for controlling the waste gate may not be provided. Consequently, the waste gate may stay in its normally closed position where boost may not be adjusted.
A waste gate may also be operated via an electric actuator. The electric actuator may be adjusted whether or not there is intake manifold pressure. Thus, boost may be regulated independent of whether or not vacuum is available or being produced. However, operation and control of electrically actuated waste gates may be influenced by other factors such as temperature and noise factors including but not limited to supply voltage variation, manufacturing variation, and engine output variation. Further, it may be challenging to provide precise waste gate position control in conjunction with providing a desired level of response.
The inventors herein have recognized the above-mentioned limitations and have developed a waste gate operating method, comprising: controlling an electronically actuated waste gate including adjusting waste gate actuation responsive to turbocharger thermal expansion and contraction.
By adjusting parameters of an electric waste gate controller for thermal conditions, it may be possible to improve waste gate position control. Further, by considering temperatures around and at the waste gate, it may be possible to operate the waste gate such that the possibility of waste gate actuator degradation is reduced.
The present description may provide several advantages. In particular, the approach may improve boost control by arriving at a desired boost pressure in a more responsive manner. Further, the approach may improve boost pressure control accuracy and repeatability. Additionally, the approach may reduce the possibility of waste gate actuator degradation.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.